Redra, Sandro and Sasha are pretty much a must for a mono skeelz deck.
Chiara is a great card
For ELO, I like Greem as my 4 star because how much for life they have and she can do alot of damage.
Personally I like Andy more than Plunk, but i still have to try him.
I also have been trying Michael and he is working well.

I'll see how Andy works when I get him, but I really like the bluff potential of Plunk.

I like Greem, too, but I don't like how her threat can reduce over time. Her poison is one of the best, though, and I do use her often. Falk is a little less bound by context, I find him useful more often. Still, there's no denying how much of a threat Greem can be,

You're right, though, it's all preference based. I don't like confidence or courage, but I really like revenge for instance.